RFC mmc: Soft Command queue implementation for eMMC5.1 device

Hello,

Seems community already have some implementation for the eMMC5.1 device command queue feature, but that require the eMMC host controller to support CMDQ. In my platform, I don't have this kind of eMMC host controller but I have a Samsung eMMC5.1 device which can support the Command queue.

With this limitation, I have to let eMMC host controller to manually send the CMD44/45/13/46/47. So in this way, more commands are needed for an I/O request, more interrupts/schedule are needed in driver.

Even this way have some more software overhead, but it can still use the eMMC5.1 device Command queue feature. After test with the iozone command:
"iozone -zec -t 4 -i0 -i2 -F iozonefile1 iozonefile2 iozonefile3 iozonefile4 -+n -I -r 4k -s 500m -O -R -+r -+D" to test random performance, I saw a performance improvment for random read on my eMMC5.1 device:

Random read
SW CMDQ: 5544.6
Normal Read: 3993.05

So I want to send this serial patches as RFC patch for reviewing

Chuanxiao Dong (5):
mmc: replace sbc to precmd and add postcmd
mmc: host: add runtime PM for host class dev
mmc: queue: change mqrq_cur and mqrq_pre to mq qdepth
mmc: core: add support for CMDQ feature in MMC Core stack
mmc: sdhci: add SW CMDQ support for CHT SDHCI host

 drivers/mmc/card/block.c      |  538 ++++++++++++++++++++++++++++++++++++++---
 drivers/mmc/card/queue.c      |  213 ++++++++--------
 drivers/mmc/card/queue.h      |   14 +-
 drivers/mmc/core/core.c       |   78 +++++-
 drivers/mmc/core/host.c       |   14 ++
 drivers/mmc/core/mmc.c        |   43 +++-
 drivers/mmc/host/dw_mmc.c     |    8 +-
 drivers/mmc/host/mmci.c       |   14 +-
 drivers/mmc/host/omap_hsmmc.c |   18 +-
 drivers/mmc/host/sdhci-acpi.c |    1 -
 drivers/mmc/host/sdhci-pci.c  |    1 -
 drivers/mmc/host/sdhci.c      |  137 +++++++++--
 include/linux/mmc/card.h      |    3 +
 include/linux/mmc/core.h      |    5 +-
 include/linux/mmc/host.h      |    5 +
 include/linux/mmc/mmc.h       |   21 ++
 include/linux/mmc/pm.h        |    1 +
 include/linux/mmc/sdhci.h     |    1 +
 18 files changed, 909 insertions(+), 206 deletions(-)

1.7.10.4